Field of the Invention
The present invention relates to an image capturing apparatus and a method of controlling an image capturing apparatus.
Description of the Related Art
In recent years, in image capturing apparatuses such as a digital video camera and a digital still camera, imaging with a high number of pixels and at high frame rates due to high-speed readout has become possible following improvements in image sensor sensitivity, enhancements in image processing, and increases in memory capacity. Imaging at a high frame rate has various benefits such as an increase in AF speed and improvements in video quality, and further increases in frame rate are in demand.
On the other hand, a pixel arithmetic averaging method is known as a pixel reduction method for capturing a moving image with a comparatively low number of pixels at a high frame rate using an image capturing apparatus with a high number of pixels. In the pixel arithmetic averaging method, the data rate is reduced and a high frame rate is realized by performing arithmetic averaging on multiple pixels in a specific cycle in the image sensor. Japanese Patent Laid-Open No. 2010-259027 discloses the output of the arithmetic average of image signals from multiple rows by using a row selection circuit to select and output signals from multiple pixel rows at the same time.
However, in the case in which multiple pixel rows are selected simultaneously and connected, there are cases in which the dynamic range can no longer be ensured. This issue becomes prominent particularly in cases in which there is a large difference in signals between simultaneously connected pixels. For this reason, in Japanese Patent Laid-Open No. 2010-259027, the dynamic range is ensured by increasing the current value for driving the pixels that perform signal output according to the number of rows simultaneously connected, and raising the driving capacity of the amplifier circuit. However, there is an issue of an increase in power consumption during readout due to the raising of the current value for driving the pixels.